A breath alcohol measuring device of this type has become known from DE 195 45 794 C2, in which the breathing gas flow within the mouthpiece is split into a main gas stream flowing directly to the environment and a measuring gas stream. The measuring gas stream is sent through the sampling system of the device and set due to the design embodiment of the device in terms of the flow volume to a value that corresponds to that delivered by prior-art calibrating devices, so that calibration of the sampling system is possible under real flow conditions. The drawback of this prior-art measuring device is the lack of hygiene and the condensation of the breathing gas stream during the direct flow of the split measuring gas stream through the sampling system.
Another breath alcohol measuring device of this type is disclosed in EP 0 153 883 A2, in which it is especially difficult to attach the mouthpiece with circular cross section to the measuring device.